System for improving operation of electrical hygrometers in radiosondes



June 29, 1948. c. B. FEAR, JR

SYSTEM FOR IMPROVING OPERATION OF ELECTRICAL HYGROMETERS IN RADIOSONDES Filed June 15 1945 /O *5 vWM/Vv I V /a 4 26 p36 TO MODULA- TOR emu ELECT/WC 0 ig HR HYGROMETL'I? i I I. LR.

I R/ 8 g. /6 Q I\ I 6 TEMPfRATl/RE SENS/T/I/E RES/670R CHARLzS 5. pAR,J/?.

m da /0m 9 M Patented June 29, 1948 SYSTEM FOR IMPROVING OPERATION OF ELECTRICAL HYGROMETERS IN RADIO- SONDES Charles B. Pear, Jr., College'Park, Md assignor to Washington Institute of'Technology, Inc., Washington, D. 0., a corporation of Delaware Application June 15, 1945, Serial No. 599,731

1 Claim.

This invention relates .tothe-art of radiosonding, by which is meantthe radiation, from a transmittercarried aloft'bya balloon, of signals "which are caused to vary in accordance with changes-in atmospheric conditions such as humidity, temperature and pressure, the reception of such signals onithe ground and the interpretation of such signals to record atmospheric I conditions at various altitudes.

and comprising in general a film of hygroscopic material on a non-hygroscopic support, deteriorate in use in the radiosonde. I have found that this deterioration is due at least in part to the fact that in known radiosonde circuits the flow of current through the conducting film of .the humidity responsive element is in a single direction. I have also found that the observed deterioration of the humidity responsive film may be prevented by periodically reversing the current therethrough.

It is therefore the principal object of this invention to provide a radiosonde including an electric hygrometer of the type referred to and an energizing circuit therefor which is so operative that the current flow through the humidity-sensitive film of the hygrometer is periodically reversed, whereby the observed deterioration which is referred to above, is prevented or retarded.

Other objects and features of novelty of the invention will be made apparent by the following description and the annexed drawing which, it will be understood, are only illustrative of the invention and impose no limitation thereon not imposed by the appended claim.

The single figure of the drawing discloses that part of the circuit of a radiosonde including the electric hygrome ter and the energizing circuit therefor. This circuit comprises temperaturesensitive resistor 2, electric hygrometer 4, relay 6, switch means 8 and resistors l0, l2 and 14. The switch means 8 is actuated by the pressure sensitive element of the radiosonde and the contact arm of this switch means is successively opcmcircuited, connected to contact RI, open-circuited, connected to contact LR, open-circuited, and connected to contact HR, in accordance with a program sequence determined by the connection of the contacts in the pressure sensitive element. When switch means 8 is open-circuited the coil I6 of relay 5 is not energized and contact arm 18 is connected to contact 20 .and contact arm 22 is connected to contact 24. Under these circumstances, twocircuits are completed. The first of these is a circuit from the modulator-grid through resistors 12 and I4 and temperaturesen-sitive resistor 2 to the -A, -B terminal of. the battery. This causes modulation of the radiosonde signal in accordance with the value of the temperature sensitive resistor 2. The second circuit is from the positive terminal of the-B battery, through resistor 10, contact arm 22 and contact 24 of relay 6, humidity sensitive resistor 4 and back to the negative terminal of the B battery, the value of the current in this circuit being controlled by proper choice of resistor 10. This current flows in the direction indicated by arrow 26. When by operation of the pressure sensitive device switch means 8 is connected to terminal RI, a circuit is completed from the positive terminal of the Alba'ttery, through coil 16 of relay :3 and switch means 8 to the minus terminal of the A battery. This energizes relay 6 and causes contact arm ill to disconnect from contacts 20 and connect to contact 28, and contact 22 to disconnect from contact 24. Under this condition the circuit from the modulator grid is connected through resistors 12 and I4 and humidity sensitive resistor 4 to the -A, B terminal of the battery. This causes the signal of the radiosonde to be modulated in accordance with the value of humidity sensitive resistor 4. Under these circumstances current flows through the circuit comprising resistors 12 and I4 and humidity sensitive resistor 4 in the direction indicated by arrow 3t. It will be seen that this current is in the opposite direction to the current flowing when the relay 6 is dc-energized.

When switch means 8 is connected to contact LR the relay 6 is de-energized and the modulator grid circuit is returned to the A, B terminal through resistors 12 and I4. This causes the transmission of a reference signal by the radiosonde. The circuit from the plus B contact of the battery through resistor Ill, contact arm 22 and contact 24 of relay 6 and humidity sensitive resistor 4 is again completed causing current to flow through the humidity-sensitive resistor 4 in the direction of arrow 26. When switch means .8 is on the contact marked HR. the conditions are exactly the same except that resistor 12 is eliminated from the modulator grid circuit thus causing a different reference signal to be transmitted by the radiosonde.

Thus, it will be seen that when the humidity signal is transmitted current flows through the humidity sensitive resistor 4 in the direction of the arrow 30, while at all other times current flows through humidity sensitive resistor 4 in the opposite, direction indicated by arrow 26, thus causing periodic reversal of the current through the resistor 4 and preventing the deteriorating effects referred to above. resistance I enables the current in the direction 26 to be adjusted to compensate-for the deteriorating effects produced by the current flowing in the direction of arrow 30.

ture therein, and means for retarding such deterioration of said device comprising a. second sage of uni-directional current in said second Proper choice of the 1 While I have described and illustrated one iomn,

which my invention may take, it will be understood by those skilled in the art that other embodiments may be made, as well as modifications the limits of which reference must be had to the appended claim.

, What is claimed is:

A radiosonde comprising an electric circuit, a

- device comprising a supporting member and a film thereon which varies in electrical resistance with the amount of moisture therein and which is caused to deteriorate by the uni-directional passage of current therethrough, means for pcriodically connecting said film in said circuit to produce a uni-directional current therein the strength of which is dependent on the resistance of said film and therefore on the amount of moiscircuit and through said mm in a direction opposite to that of the first current.

CHARLES B. PEAR, JR-

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 941,777 Hart Nov. 30, 1909 1,176,794 U'hl Mar. 28, 1916 1,383,233 Parsons et al June 28, 1921 1,749,826 Lu bach Mar. 11, 1930 2,285,421 Dunmore June 9, 1942 2,295,570 Dunmore Sept. 15, 1942 2,375,609 Zulke May 8, 1945 2,381,009 Siderman Aug. 7, 1945 2,418,836 HEUWES Apr. 15, 1947 FOREIGN PATENTS Number Country Date Great Britain Apr. 2, 1942 

